1. Field of the Invention
The present invention generally relates to an indexable end mill wherein an indexable insert is mounted to a round distal end portion of an end mill body as protruded from the end mill body and also relates to the indexable insert mounted to the indexable end mill.
2. Description of the Related Art
As one type of cutting tool, there has conventionally been employed an indexable end mill arranged such that, as shown in FIG. 1, an indexable insert 2 is mounted to a round distal end portion of an end mill body 1 as protruded from the end mill body 1.
As shown in FIGS. 1 and 2, the prior-art indexable insert mounted to the distal end portion of such an end mill body 1 has a substantially elliptical shape in plan, including a mounting hole 2b defined at a center of its cutting face 2a for mounting the indexable insert 2 to the end mill body 1 by means of a screw 3, and two cutting edges 2c each formed in an arcuate shape.
The indexable end mill with the indexable insert 2 protruded from the end mill body 1 has been used for cutting a workpiece (not shown) in a manner such that the indexable end mill is rotated with the indexable insert 2 pressed against the workpiece thereby cutting the workpiece from the top like a drill.
In order to perform the cutting work by means of the indexable insert 2, which is pressed against the workpiece as protruded from the distal end portion of the end mill body 1, it is common practice in the art to form end faces 2d at opposite ends of the indexable insert 2 where the two cutting edges 2c intersect each other. That is, each end face 2d is formed by cutting away an end portion of the cutting face 2a corresponding to a rotation center of the indexable end mill rotated for cutting the workpiece, the cut-away portion being in a bent form extended from a place corresponding to the rotation center of the end mill body. The indexable insert 2 is arranged such that chip removed by the cutting edge 2c at a rotation-center portion of the indexable insert is guided along the end face 2d to the cutting face 2a for discharge.
Unfortunately, when the indexable end mill is cutting the workpiece as pressed thereagainst, the chip removed by the cut-away portion of the insert of the indexable insert 2 disposed substantially on the rotation axis of the end mill is held by a face 2e rising from the end face 2d to the cutting face 2a so that the cut-away portion of the indexable insert 2 becomes blocked with the removed chip which, in turn, is fused thereto.
If, in this state, the indexable end mill is kept rotating for the cutting work, the indexable insert 2 is subject to an excessive load, resulting in a breakage thereof or a reduced cutting performance thereof which lowers the cutting precision of the end mill. As a result, the end mill cannot ensure stability and high precision of the cutting work.